1. Field of the Invention
The present invention relates to a bendable joint mechanism.
2. Description of the Related Art
Hitherto, as a bendable joint mechanism, there has generally been known one that has a single rotating shaft (joint shaft), i.e. a one-degree-of-freedom rotary type joint mechanism. In this type of joint mechanism, two members are connected so as to be relatively rotatable about a single rotating shaft.
For example, Japanese Patent Application Laid-Open No. 2012-90849 describes a knee joint of a walking assist mechanism that uses the one-degree-of-freedom rotary type joint mechanism described above.
Meanwhile, a joint, such as a human knee joint, does not have a fixed single joint axis, and the position of an instantaneous rotational center changes to accomplish bending at the joint.
Accordingly, an attempt to generate power for assisting the bending and stretching at such a joint by a joint mechanism having a fixed single joint tends to cause a situation in which the motion of a human joint and the motion of the joint of the joint mechanism do not fully match. This frequently causes a person wearing the joint mechanism to feel uncomfortable or awkward mainly due to a force acting to interfere with a desired motion of the joint.
In order to eliminate such an inconvenience, a joint mechanism best suited for each person could be individually prepared, or a structure or the like for connecting a joint mechanism to each person could be designed to be adjustable according to each person.
However, if a dedicated joint mechanism were prepared for each individual, then the joint mechanism would be costly.
Further, if the structure of a joint mechanism were designed to be adjustable for each individual, then the structure of the joint mechanism would tend to be complicated or become larger. In addition, there would be some cases where the joint mechanism could not be satisfactorily suited to each individual, depending on his or her body shape or the like.